Hitherto, there has been used a stapleless binding apparatus having the following configuration. The stapleless binding apparatus stacks a plurality of sheets and sandwiches the plurality of sheets with a strong pressure between a pair of clamping teeth each having a corrugated shape, to thereby clamp the sheets and bind a sheet bundle without use of a metal staple. This stapleless binding apparatus has a problem in that the sheet bundle adheres to one of the clamping teeth when the clamping teeth are to be separated.
In Patent Literature 1, there is disclosed a sheet bundle binding apparatus having the following configuration. In the sheet bundle binding apparatus, side alignment members configured to uniformly align a sheet bundle on a processing tray in a direction orthogonal to a sheet delivery direction are used to kick or thrust out a sheet bundle, which has been subjected to binding, from a side to separate the sheet bundle from a pressing surface of a stapleless binding portion. The side alignment members are driven by an alignment motor so as to once perform a back-swing motion to positions away from positions of being engaged with sheet side edges. After that, the side alignment members move to a sheet center side to kick the sheet bundle. Further, in Patent Literature 2, there is disclosed a post-processing mechanism having the following configuration. The post-processing mechanism stacks sheets from a sheet delivery port of an image forming apparatus onto a processing tray and allows an operator to select which of staple binding and stapleless binding to be performed to the sheet bundle.